Parathyroid hormone independent renal phosphate wasting has been observed in children with chronic cholestatic liver disease. A correlation between this loss from the phosphate pool and bone density is hypothesized. Age appropriate control groups for renal phosphate handling and bone density (dual photon absorptiometry) will be established. Data from children with protracted cholestasis and from children with malabsorption due to other causes (e.g., cystic fibrosis) can then be compared to the control data.